It is known to provide perimeter fence structures around installations such as an oilfield drilling site or wellhead. The perimeter fence must effectively prevent animal encroachment, particularly by cattle, as many of these installations are found on agricultural range land.
Cattle are known to rub against conventional fencing, such as wire or wire mesh panels having vertical posts. Over time, the constant rubbing results in damage and disruption of the integrity of the fence.
Further, modular fence structures are typically moved from site to site such as when drilling ends or wells no longer produce. Thus, it is of some considerable importance that the perimeter fence structures are modular and are easily transported in conventional pickup trucks or on towed trailers. Onsite, access to the enclosed installation may be required by large equipment such as service rigs. It is advantageous if the fence assemblies are readily connected and disconnected from each other to provide access when required.
As many drilling sites are located in areas which are subject to below-freezing ambient temperatures, it is also important that the modular assemblies used to create the perimeter fence are not secured to the ground in such a fashion that the fastenings become frozen into the ground. Removal of frozen fastenings often results in damage to both the fastenings and to the fence assemblies.
U.S. Pat. No. 5,533,714 to St. John teaches a modular fence apparatus for use in constructing a perimeter fence to prevent entry of animals and cattle into the fenced area. The fence apparatus comprises flat panels with span members. The flat panels are connected to discrete corner assemblies that are angled so as to set each panel at an angle. The panels are angled inward along a top edge. Further, the corner assemblies have span members connected between frame members to form triangular angled corner panels. While the flat panels are easily stacked for transport, the corner assemblies, which comprise three upright posts, 2 angled top members and the span members, are awkward and not readily stacked. Each flat panel must be connected at each end to a corner assembly using fasteners when the perimeter is assembled and similarly, fasteners must be removed to gain access for large equipment or for disassembly. If the perimeter fence is required to be other than rectangular, separate corner assemblies would be required having various preset angles.
Canadian patent 1,091,968 to Hillman teaches a perimeter fence having generally vertically disposed rigid post members which have a lower portion that engages the ground and an upper, inwardly inclined portion to which the rails are attached. At least one of the rails is disposed at the height of the average bovine knee to prevent leaning or rubbing. Rails, extending at right angles to the corner posts, are welded or otherwise fastened to the corner posts. The rails are split mid-span and connected by welding, by removable fasteners or the like. Clearly, assembly on site requires significant time and effort. If formed as modules having the rails pre-welded to the corner posts, each module is relatively large and cumbersome. Transport of the modules would be awkward and the number of modules that could be transported at any one time may be limited. As with the perimeter fence of St. John, changes in the shape of the fence would require welding the rails to the corner posts at a variety of angles, necessitating on-site assembly or stocking of a number of different modules.
Clearly, what is required is a modular fence assembly that can be readily stacked for transport in a truck bed. Further, the modules should require a minimum of assembly on site and allow for forming a perimeter fence of whatever shape is required for each unique location. Preferably, the fence should be easily opened for access to large equipment such as a service rig.